Disc brakes have first and second friction members aligned by a caliper on opposite sides of a rotor that is attached to an axle retained in a bearing held in a housing of a vehicle. The friction members are urged into frictional engagement with the rotor to effect a brake application of a vehicle. The frictional engagement causes the first and second friction members to wear and after a period of time are worn such that it is necessary to replace the first and second friction members. Wear of the friction members is usually communicated to an operator through a wear indicator of which the indicators disclosed in U.S. Pat. Nos. 4,745,992; 4,067,418; 4,460,067 may be considered as being typical. In such wear indicators, an arm member that is connected to a backing plate for a friction member and during a brake application contacts the braking surface on the rotor to create a squeal sound or noise. Unfortunately, the squeal sound often is unsatisfactory as the sound is too soft or similar to other sounds created during engagement of a brake pad with the rotor and as a result a delay occurs in the communication of this information to an operator. Further, once the arm member engages the rotor it is possible to scratch and mar the rotor braking surface in such a manner that unnecessary re-facing must be performed before replacement with new first and second friction members occurs.
A primary object of the present invention is to provide a disc brake with indicator means that produce a distinctive clicking sound when a predetermined wear of the friction members occurs so that an operator will instinctively associate the clicking sound with a need to replace the friction members in the disc brake.
According to this invention, the disc brake assembly has a support member that is secured to a vehicle. A caliper retained in the support member has an actuation section that is connected by a bridge to an arm. The actuation section has an actuation bore therein for retaining a piston to define an actuation chamber. A first friction member is connected to the piston and aligned with a first braking surface on a rotor associated with a wheel on the vehicle. A second friction member is connected to the arm and aligned with a second braking surface on the rotor. The actuation chamber on being presented pressurized fluid from a source acts on the piston to develop an actuation force that moves the piston and first friction member toward and into engagement with the first braking surface and acts on the actuation section such that the caliper moves the second friction member into engagement with the second braking surface to effect a brake application. The first and second friction members have a first initial thickness and the rotor has a second initial thickness. With each brake application the first and second initial thickness change as the first and second friction members and said rotor are worn away to define an instant thickness. An indicator arrangement includes a clip member that is secured to one or both of the first and second friction members having an arm that engages the rotor to inform an operator when an instant thickness is equated to a predetermined thickness corresponding to a thickness where the first and second friction member need to be replaced. The indicator arrangement is characterized in that the rotor includes a plurality of projections that extend from the rotor at a location adjacent to one of the first and second braking surfaces. When the predetermined instant thickness occurs the arm engages the plurality of projections to create a clicking noise that distinctly identifies to an operator optimum braking of the vehicle may not be achieved with the present first and second friction member and rotor.
An advantage of the disc brake of this invention resides in projections that extend from a rotor for an arm of a clip member to engage and create a distinct sound to inform an operator of a wear condition of friction members.
A further advantage of this disc brake resides in the coating of a sound generation arrangement to protect the components from corrosion at least until engagement occurs after a predetermined wear of the friction members.